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Journal of Bacteriology, November 2006, p. 7521-7530, Vol. 188, No. 21
0021-9193/06/$08.00+0     doi:10.1128/JB.00943-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Posttranslational Modification of the 20S Proteasomal Proteins of the Archaeon Haloferax volcanii ^,

Matthew A. Humbard,¹ Stanley M. Stevens Jr.,² and Julie A. Maupin-Furlow^1*

University of Florida, Department of Microbiology and Cell Science, Gainesville, Florida 32611-0700,¹ University of Florida, Proteomics Core Facility, ICBR, Gainesville, Florida 32610-0156²

Received 29 June 2006/ Accepted 20 August 2006

20S proteasomes are large, multicatalytic proteases that play an important role in intracellular protein degradation. The barrel-like architecture of 20S proteasomes, formed by the stacking of four heptameric protein rings, is highly conserved from archaea to eukaryotes. The outer two rings are composed of -type subunits, and the inner two rings are composed of ß-type subunits. The halophilic archaeon Haloferax volcanii synthesizes two different -type proteins, 1 and 2, and one ß-type protein that assemble into at least two 20S proteasome subtypes. In this study, we demonstrate that all three of these 20S proteasomal proteins (1, 2, and ß) are modified either post- or cotranslationally. Using electrospray ionization quadrupole time-of-flight mass spectrometry, a phosphorylation site of the ß subunit was identified at Ser129 of the deduced protein sequence. In addition, 1 and 2 contained N-terminal acetyl groups. These findings represent the first evidence of acetylation and phosphorylation of archaeal proteasomes and are one of the limited examples of post- and/or cotranslational modification of proteins in this unusual group of organisms.

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* Corresponding author. Mailing address: Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611-0700. Phone: (352) 392-4095. Fax: (352) 392-5922. E-mail: jmaupin{at}ufl.edu.

Published ahead of print on 1 September 2006.

Supplemental material for this article may be found at http://jb.asm.org/.

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Journal of Bacteriology, November 2006, p. 7521-7530, Vol. 188, No. 21
0021-9193/06/$08.00+0     doi:10.1128/JB.00943-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

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• Kirkland, P. A., Gil, M. A., Karadzic, I. M., Maupin-Furlow, J. A. (2008). Genetic and Proteomic Analyses of a Proteasome-Activating Nucleotidase A Mutant of the Haloarchaeon Haloferax volcanii. J. Bacteriol. 190: 193-205 [Abstract] [Full Text]  
• Kirkland, P. A., Reuter, C. J., Maupin-Furlow, J. A. (2007). Effect of proteasome inhibitor clasto-lactacystin-beta-lactone on the proteome of the haloarchaeon Haloferax volcanii. Microbiology 153: 2271-2280 [Abstract] [Full Text]